<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <script>
    function recursion(num) {
      if (num < 0) {
        return '输入的数字不能小于0';
      } else if (num == 0) {
        return 0;
      } else if (num == 1) {
        return 1;
      } else if (num > 1) {
        return recursion(num - 1) + recursion(num - 2);
      }
    }
    console.log(recursion(10));
  </script>
</body>
</html>